Historical surface records(T-S-density)

NE Atlantic subpolar gyre-Corridor of the northward upper layer transport to convection sites and- this Arctic,Subsurface hydrographic changes i(correlated to the surface) indicate large water mass changes related to advection in recent decades (in addition to local transformation from the air-sea heat fluxes)

- fragmentary indications from proxi records that this has happened in the recent past (1920s) through parts of the holocene (Feni drift forams, deep-sea cold corals…), but time scales of the variability not always that clear.

-Extending the historical record-- long time series stations through FS Channel-- larger scale analysis of surface data (potentially less noisy, and covers a larger part of the northward transport)

Eastern part of the subpolar gyreSensitive to extension fluctuations (gyre circulation)Inter-gyre gyre and MOC intensity

Large variability documented in the 1970-2005 period...

Norhtward branches

Ride de ReykjanesThe northward branches

Areas regularly sampledVOS – time series stations

(less in winter, gaps WWI and WW2)

The data sets

Corrected ship-of-opportunity sample data before 1960 (or 1974)(both T and S); some doubts on S correction in 1920s and 1945-55; T correction less than in HadSST2.

Validated ship-of-opportunity TSG data since 1994;

Other data: no correction…

Time series created separately for different seasons and boxes.Correlation between March-May and June-July (both for T and S)and spatially across the domain.

T very similar to HadSST2 (except warming tendency larger), and average of the boxes similar.

S presents small negative tendency (-0.035 psu) but changes in data/methods: uncertainties in standarts before 1905; Ways of sampling and measure…positive errors before WWII and negative errors since the mid-1990s; chlorinity or conductivity derived)

Combining the time series(that are correlated)Filtering decennalAnd multi-decennal (cut-off 18 years)

T-S decennal dont Correlate well (after 1970)(frequency change for T in late 1960sAmplitude change for S 1950-1990

Different seasons(slightly larger signalIn late summer)

T-S correlated; Notice, however, the difference in the1920s

Relation to NAO (or changes inWeather regimes, or large westerliesPeriods

Multi-decennal correlated at 0 or 1 yr lag

HF, S correlated with 2-3 yr lags.For T, correlation at 0 lag before 1960;Very weak and 3 year lag after